DESCRIPTION: (Adapted from applicant?s abstract): This project proposes to systematically investigate linkage disequilibrium in human populations. Data to be collected consist of haplotypes spanning 200-500 kb at eight independent loci in 20 populations. The eight loci, which are a subset of the 20 loci investigated in Project 1, will include centromeric, telomeric, and mid-arm chromosomal regions, in order to investigate systematic influences of chromosomal regions on linkage disequilibrium. The 20 populations, which are identical to the 20 populations analyzed in Project 1, will comprise a representative sample of global human diversity, in order to minimize idiosyncratic influences of particular population histories on linkage disequilibrium. Initially, a number of polymorphic markers will be identified and typed in a 200 kb region of each locus. Additional markers will then be added to allow the total region to be spanned in each locus to be adjusted either upwards (to a maximum of 500 kb) or downwards, depending on the amount of linkage disequilibrium found in the initial survey of 200 kb from each locus. The stated goal is to evaluate the amount and distribution of recombination across each locus, and the relative influence of shared vs. independent population histories, in shaping the overall pattern of linkage disequilibrium across the 160 population-locus combinations.